The upgrade to Wazo 18.01 or later will take longer than usual, because the whole Debian system will
be upgraded.

The database management system (postgresql) will also be upgraded from version 9.4 to version 9.6 at
the same time. This will upgrade the database used by Wazo. This operation should take at most a
few minutes.

Check that customization to your configuration files is still effective.

During the upgrade, new version of configuration files are going to be installed, and these might
override your local customization. For example, the vim package provides a new /etc/vim/vimrc
file. If you have customized this file, after the upgrade you’ll have both a /etc/vim/vimrc and
/etc/vim/vimrc.dpkg-old file, the former containing the new version of the file shipped by
the vim package while the later is your customized version. You should merge back your
customization into the new file, then delete the .dpkg-old file.

You can see a list of affected files by running find/etc-name'*.dpkg-old'. If some files
show up that you didn’t modify by yourself, you can ignore them.

Purge removed packages. You can see the list of packages in this state by running dpkg-l|awk'/^rc/{print$2}' and purge all of them with apt-getpurge$(dpkg-l|awk'/^rc/{print$2}')

Reboot your system. It is necessary for the new Linux kernel to be effective.

Here’s a non-exhaustive list of changes that comes with Wazo on Debian 9:

Network interface names (only for new installs, not upgrades): Debian Stretch uses the new
standard naming scheme for network interfaces instead of eth0, eth1, etc. The new
enumeration method relies on more sources of information, to produce a more repeatable outcome. It
uses the firmware/BIOS provided index numbers and then tries PCI card slot numbers, producing
names like ens0 or enp1s1.